Candidate Genes for Eyelid Myoclonia with Absences, Review of the Literature

Eyelid myoclonia with absences (EMA), also known as Jeavons syndrome (JS) is a childhood onset epileptic syndrome with manifestations involving a clinical triad of absence seizures with eyelid myoclonia (EM), photosensitivity (PS), and seizures or electroencephalogram (EEG) paroxysms induced by eye closure. Although a genetic contribution to this syndrome is likely and some genetic alterations have been defined in several cases, the genes responsible for have not been identified. In this review, patients diagnosed with EMA (or EMA-like phenotype) with a genetic diagnosis are summarized. Based on this, four genes could be associated to this syndrome (SYNGAP1, KIA02022/NEXMIF, RORB, and CHD2). Moreover, although there is not enough evidence yet to consider them as candidate for EMA, three more genes present also different alterations in some patients with clinical diagnosis of the disease (SLC2A1, NAA10, and KCNB1). Therefore, a possible relationship of these genes with the disease is discussed in this review

CfDNA Measurement as a Diagnostic Tool for the Detection of Brain Somatic Mutations in Refractory Epilepsy

Epilepsy is a neurological disorder that affects more than 50 million people. Its etiology is unknown in approximately 60% of cases, although the existence of a genetic factor is estimated in about 75% of these individuals. Hundreds of genes involved in epilepsy are known, and their number is increasing progressively, especially with next-generation sequencing techniques. However, there are still many cases in which the results of these molecular studies do not fully explain the phenotype of the patients. Somatic mutations specific to brain tissue could contribute to the phenotypic spectrum of epilepsy. Undetectable in the genomic DNA of blood cells, these alterations can be identified in cell-free DNA (cfDNA). We aim to review the current literature regarding the detection of somatic variants in cfDNA to diagnose refractory epilepsy, highlighting novel research directions and suggesting further studies

Desarrollo de un protocolo integral de secuenciación masiva para el diagnóstico prenatal de aneuploidías en plasma materno

Tesis doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Biología. Fecha de lectura: 03-12-2021En base al descubrimiento del ADN fetal libre circulante (ADNfl) en sangre materna y el posterior desarrollo de la secuenciación masiva, se ha establecido como método de cribado de aneuploidías el Test Prenatal No Invasivo (TPNI). Consiste en determinar la presencia de anomalías cromosómicas numéricas utilizando para ello una muestra de plasma materno. En España no existen protocolos que definan las indicaciones concretas o el abordaje metodológico más adecuado para realizarlo. El objetivo principal de esta tesis consiste en desarrollar una aproximación metodológica y funcional válida para su implementación en el ámbito clínico. Para ello, se ha realizado un análisis de coste/eficacia en relación con el cribado combinado de aneuploidías del primer trimestre. Además, se han analizado, de manera pormenorizada, las indicaciones reflejadas en los protocolos de las principales sociedades científicas estableciendo diferentes escenarios en base a la distribución de nuestra población. Adicionalmente, se han analizado en profundidad diferentes métodos de análisis, incluyendo una aproximación de desarrollo propio, con objeto de determinar su rendimiento diagnóstico, aplicabilidad y robustez. Para ello, se han estudiado 229 muestras mediante secuenciación por semiconductores en abordaje de genoma completo y 264 muestras mediante secuenciación por síntesis, realizando una aproximación dirigida a las regiones de interés. Los resultados consecuencia en este proceso, se han analizado mediante tres herramientas informáticas, obteniéndose los mejores resultados mediante la utilización de secuenciación de genoma completo. La reducción de costes de la secuenciación masiva, la acumulación de datos que demuestran la superior eficacia del TPNI sobre el cribado convencional y la mayor concienciación de las autoridades, apuntan hacia el logro potencial del TPNI universal para el cribado de aneuploidías frecuentes sin aumentar el coste general de la atención médica prenatal. Además, el análisis del genoma fetal a partir de ADN circulante en sangre materna abre la puerta a futuros avances en el conocimiento del estatus genético feto-placentario que permitan identificar alteraciones implicadas en el correcto desarrollo del embaraz

Noninvasive Prenatal Testing: Comparison of Two Mappers and Influence in the Diagnostic Yield

Objective. The aim of this study was to determine if the use of different mappers for NIPT may vary the results considerably. Methods. Peripheral blood was collected from 217 pregnant women, 58 pathological (34 pregnancies with trisomy 21, 18 with trisomy 18, and 6 with trisomy 13) and 159 euploid. MPS was performed following a manufacturer’s modified protocol of semiconductor sequencing. Obtained reads were mapped with two different software programs: TMAP and HPG-Aligner, comparing the results. Results. Using TMAP, 57 pathological samples were correctly detected (sensitivity 98.28%, specificity 93.08%): 33 samples as trisomy 21 (sensitivity 97.06%, specificity 99.45%), 16 as trisomy 18 (sensibility 88.89%, specificity 93.97%), and 6 as trisomy 13 (sensibility 100%, specificity 100%). 11 false positives, 1 false negative, and 2 samples incorrectly identified were obtained. Using HPG-Aligner, all the 58 pathological samples were correctly identified (sensibility 100%, specificity 96.86%): 34 as trisomy 21 (sensibility 100%, specificity 98.91%), 18 as trisomy 18 (sensibility 100%, specificity 98.99%), and 6 as trisomy 13 (sensibility 100%, specificity 99.53%). 5 false positives were obtained. Conclusion. Different mappers use slightly different algorithms, so the use of one mapper or another with the same batch file can provide different results

Fragile X Syndrome Caused by Maternal Somatic Mosaicism of <i>FMR1</i> Gene: Case Report and Literature Review

Fragile X syndrome (FXS) is caused by an abnormal expansion of the number of trinucleotide CGG repeats located in the 5′ UTR in the first exon of the FMR1 gene. Size and methylation mosaicisms are commonly observed in FXS patients. Both types of mosaicisms might be associated with less severe phenotypes depending on the number of cells expressing FMRP. Although this dynamic mutation is the main underlying cause of FXS, other mechanisms, including point mutations or deletions, can lead to FXS. Several reports have demonstrated that de novo deletions including the entire or a portion of the FMR1 gene end up with the absence of FMRP and, thus, can lead to the typical clinical features of FXS. However, very little is known about the clinical manifestations associated with FMR1 gene deletions in mosaicism. Here, we report an FXS case caused by an entire hemizygous deletion of the FMR1 gene caused by maternal mosaicism. This manuscript reports this case and a literature review of the clinical manifestations presented by carriers of FMR1 gene deletions in mosaicism

Towards a Change in the Diagnostic Algorithm of Autism Spectrum Disorders: Evidence Supporting Whole Exome Sequencing as a First-Tier Test

Autism spectrum disorder (ASD) is a prevalent and extremely heterogeneous neurodevelopmental disorder (NDD) with a strong genetic component. In recent years, the clinical relevance of de novo mutations to the aetiology of ASD has been demonstrated. Current guidelines recommend chromosomal microarray (CMA) and a FMR1 testing as first-tier tests, but there is increasing evidence that support the use of NGS for the diagnosis of NDDs. Specifically in ASD, it has not been extensively evaluated and, thus, we performed and compared the clinical utility of CMA, FMR1 testing, and/or whole exome sequencing (WES) in a cohort of 343 ASD patients. We achieved a global diagnostic rate of 12.8% (44/343), the majority of them being characterised by WES (33/44; 75%) compared to CMA (9/44; 20.4%) or FMR1 testing (2/44; 4.5%). Taking into account the age at which genetic testing was carried out, we identified a causal genetic alteration in 22.5% (37/164) of patients over 5 years old, but only in 3.9% (7/179) of patients under this age. Our data evidence the higher diagnostic power of WES compared to CMA in the study of ASD and support the implementation of WES as a first-tier test for the genetic diagnosis of this disorder, when there is no suspicion of fragile X syndrome